In general, a motor includes a stator and a rotor, and the rotor has various kinds and forms. The present invention relates to a rotor having a permanent magnet embedded inside a rotor core.
A rotor 100 having the above form according to a prior art is illustrated in FIG. 1.
As shown in FIG. 1, the rotor 100 according to the prior art includes a rotor core 110 in which a plurality of magnets (not shown) are inserted, and a molding part 120 made of plastic resin, such as PBT resin and formed around the core 110. A shaft 50 joined to a central portion of the rotor core 110 is rotated by the rotation of the rotor core 110 to rotate a load connected to the shaft.
In the conventional rotor 100, the molding part 120 surrounding the rotor is formed through the steps of inserting the rotor core 110 into a mold and performing insert injection molding. As described above, the process of manufacturing the molding part 120 through the insert injection molding has the following problems.
First, because the mold of the rotor shape must be manufactured for the insert injection molding, it cause expensive manufacturing costs and the manufacturing process is complicated.
Second, because the inside of the rotor and considerable portions of the outer face of the rotor are made of plastic resin, the rotor requires a great deal of resin and a great amount of resin is lost during the molding work, and hence, manufacturing costs are increased.
Third, the rotor core 110 is generally manufactured using laminated thin steel sheets, but in the case that thin steel sheets are not laminated exactly vertically but laminated somewhat slantly without even straightness, because the rotor core is not inserted well into the mold, the insert injection molding is impossible and there is a high defection rate.
Accordingly, the inventor of the present invention recognize the above problems of the rotor manufacturing process using the insert injection molding method, and hence, propose a new structure of a rotor, which can solve the above problems by applying not the insert molding method but a method of applying a rotor cover to the outside of the rotor.